Many equipments or devices, including, for example, mobile phones and electronic equipment, to name but a few, contain rechargeable batteries. An increasingly popular method of recharging such rechargeable batteries is wireless or inductive charging. An example of the use of wireless charging is provided in U.S. Pat. No. 8,212,518. It is common to refer to the charging apparatus as the “transmitter” or “charging pad” or “pad” and to the device or equipment being charged as the “receiver”. Both the receiver and the pad typically have respective coils between which the energy for charging the receiver's battery is transferred via inductive coupling.
In order to effectively charge the receiver, an adequate alignment between the coil of the receiver and the coil of the pad is necessary. Some pads employ fixed positioning in order to assure alignment between pad and receiver coils. Such alignment may be based upon the use of matching shapes or magnets in the pad and receiver.
Free-positioning pads allow the receiver to be positioned anywhere on the pad. Typically such a pad has an array of embedded charging coils. However, knowledge of the precise position of the receiver on the pad is required so that the appropriate coil(s) are energized in order to assure close inductive coupling between the pad and the receiver.